HAT1: The best-understood set of acetyltransferases is the GNAT (Gcn5-related N-acetyltransferase) superfamily, which have been grouped together on the basis of their similarity in several homology regions and acetylation-related motifs. This group includes the HAT Gcn5, its close relatives, and at least three more distantly related HATs, Hat1, Elp3, and Hpa2. (1)

Hat1 is the sole known example of a type B histone acetyltransferase. While it has long been presumed that type B histone acetyltransferases participate in the acetylation of newly synthesized histones during the process of chromatin assembly.